At Center of Convex Lens & Glass Plate: What is Observed?

AI Thread Summary
When a convex lens is placed on a flat glass plate and illuminated with monochromatic red light, concentric bands of red and dark are observed. At the center of the lens, where it contacts the glass plate, there is a thin layer of air that causes light to reflect at both the lens/air and air/plate boundaries. The interference between these two reflections creates a phase difference that affects the observed patterns. Understanding this phase difference is crucial for analyzing the resulting interference patterns. The discussion highlights the complexity of light behavior in this setup and the need for further exploration of the reflections involved.
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A convex lens is placed on a flat glass plate and illuminated from above with monochromatic red light. When viewed from above, concentric bans of red and dark are observed. What does one observe at the exact center of the lens where the lens and the glass plate are in direct contact.
 
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There is a thin layer of air between the surfaces, thus light reflects at the glass/air boundaries. The first reflection is at the lens/air boundary, the second at the air/plate boundary. Consider the interference between these two reflections. (What is their phase difference?)
 
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Still can't figure out :mad:
 
What have you done so far? What can you say about the two reflections?
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...

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